vendredi 12 avril 2013

ESA’s retired GIOVE-A navigation mission has become the first civilian satellite to perform GPS position fixes from high orbit. Its results demonstrate that current satnav signals could guide missions much further away in space, up to geostationary orbit or even as far as the Moon.

GIOVE-A has been able to fix its position, velocity and time from GPS signals, despite orbiting more than 1000 km above the downward-pointing US satellites.

“Satellite navigation has become almost as indispensable for most low-orbiting satellites as it is for car drivers and other terrestrial users,” says ESA’s Steeve Kowaltschek.

“GIOVE-A’s three months of data show that future geostationary satellites could operate in the same way, bringing real competitive advantage to the multi-billion-euro telecommunications satellite market.”

Long-life satellite

Launched in 2005 to claim radio frequencies and test hardware for Europe’s Galileo satnav constellation, the Galileo In-Orbit Validation Element-A, or GIOVE-A, mission far outlasted its original two-year design life.

It was formally decommissioned by ESA in the middle of last year, once the first Galileo satellites completed their orbital commissioning. Having been moved into a graveyard orbit about 100 km above Galileo’s orbital altitude of 23 222 km, control was passed to its prime contractor Surrey Satellite Technology Ltd of Guildford, UK.

GIOVE-A on the launch pad

SSTL then collaborated with ESA experts to employ the aged satellite for experimental satnav reception.

The tests used a satnav receiver that had been activated for only 90 minutes during the very beginning of the satellite’s seven-year operational life.

“We have been really encouraged by the initial results from our receiver,” said Martin Unwin at SSTL. “Our patience has finally been rewarded, and we would like to make the best of this unique opportunity.”

SSTL is able to upload new software to the receiver in orbit, and has been able to apply sophisticated software algorithms to help detect faint satnav signals.

Further work is planned to refine operation through the use of an accurate onboard clock and orbit-estimating algorithms.

Taking a sideways look

GPS satellites – like those of Galileo, Russia’s Glonass or their Japanese, Chinese and Indian counterparts – aim their antennas directly at Earth.

Side lobe satnav signals available to satellites in higher orbits

Any satellite orbiting above the GPS constellation can only hope to detect signals from over Earth’s far side, but the majority are blocked by the planet. For a position fix, a satnav receiver requires a minimum of four satellites to be visible, but this is most of the time not possible if based solely on front-facing signals.

Instead, GIOVE-A makes use of signals emitted sideways from GPS antennas, within what is known as ‘side lobes’. Just like a flashlight, radio antennas shine energy to the side as well as directly forward.

jeudi 11 avril 2013

The Large Hadron Collider (LHC) tunnel is renowned for its geological stability: set between layers of sandstone and molasse, it has allowed the world’s largest accelerators to run to sub-millimetre precision. But even the most stable of tunnels can be affected by geological events. To ensure the precise alignment of the LHC, the CERN survey team performs regular measurements of the vertical position of the magnets (a process known as “levelling”).

The team has taken measurements of the LHC before its temperature reached 100 kelvin, beyond which there may be some mechanical movements. As no data could be gathered while the machine was in operation, these measurements will provide the clearest picture yet of the accelerator's position at the end of its run. The team used a so-called “fast levelling” technique, which involves measuring every second magnet in order to complete the survey as quickly as possible and to reduce the influence of the environmental conditions that could affect the observations made with an optical level. Technicians were able not only to measure the height of the magnets but also to make immediate height comparisons with the previous magnets. No magnet realignments were carried out at this stage.

“By comparing these measurements with the base measurements taken during the 2008-2009 shutdown, we will soon have an accurate picture of how ground disturbances may have affected the machine,” says Dominique Missiaen, leader of the Beams department section responsible for large-scale metrology. “This comparison will also help us predict possible future deviations and deterioration of the relative positions between magnets.”

The next series of levelling measurements will be taken at the end of the first long shutdown, once the work on the LHC interconnects has been completed. Technicians will then perform complete levelling measurements of the machine, measuring every LHC magnet and adjusting the magnet heights when they see significant variations. “The main aim of this levelling is not to have perfect measurements of the height of the machine, but rather to have an accurate evaluation of each magnet with respect to its neighbours,” says Missiaen. “We will ensure the magnets are all smoothly aligned for the restart of the machine, as even the smallest of differences can affect the beam orbit.”

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

CERN, the European Organization for Nuclear Research

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 Member States.

NASA's FY2014 budget proposal includes a plan to robotically capture a small near-Earth asteroid and redirect it safely to a stable orbit in the Earth-moon system where astronauts can visit and explore it.

The astronauts will build on years of knowledge from the International Space Station, exploration mission concepts, scientific spacecraft and ground-based analog missions.

Robotically capture a small near-Earth asteroid

Performing these elements for the proposed asteroid initiative integrates the best of NASA's science, technology and human exploration capabilities and draws on the innovation of America's brightest scientists and engineers. It uses current and developing capabilities to find both large asteroids that pose a hazard to Earth and small asteroids that could be candidates for the initiative, accelerates our technology development activities in high-powered solar electric propulsion and takes advantage of our hard work on the Space Launch System rocket and Orion spacecraft, helping to keep NASA on target to reach the President's goal of sending humans to Mars in the 2030s.

When astronauts don their spacesuits and venture out for a spacewalk on the surface of an asteroid, how they move and take samples of it will be based on years of knowledge built by NASA scientists and engineers who have assembled and operated the International Space Station, evaluated exploration mission concepts, sent scientific spacecraft to characterize near-Earth objects and performed ground-based analog missions.

Artist's Concept of a Solar Electric Propulsion System

Using advanced Solar Electric Propulsion (SEP) technologies is an essential part of future missions into deep space with larger payloads. The use of robotics and advanced SEP technologies like this concept of an SEP-based spacecraft during NASA mission to find, rendezvous, capture and relocate an asteroid to a stable point in the lunar vicinity offers more mission flexibility than would be possible if a crewed mission went all the way to the asteroid.

Asteroid Initiative Animation

As early as the 1970s, NASA examined potential ways to use existing hardware to visit an asteroid to understand better its characteristics. On the International Space Station, scientific investigations and technology demonstrations are improving knowledge of how humans can live and work in space. The agency also has examined many possible mission concepts to help define what capabilities are needed to push the boundaries of space exploration.

During the early space shuttle flights and through assembly of the space station, NASA has relied on testing both in space and on Earth to try out ideas through a host of analog missions, or field tests, that simulate the complexity of endeavors in space.

Through 16 missions in the National Oceanic and Atmospheric Administration's underwater Aquarius Reef Base off the coast of Key Largo, Fla., aquanauts have tested techniques for human space exploration. These underwater tests have been built upon the experience gained by training astronauts in the Neutral Buoyancy Laboratory at NASA’s Johnson Space Center in Houston to assemble and maintain the space station. The NASA Extreme Environment Mission Operations (NEEMO) 15 and 16 missions in 2011 and 2012, respectively, simulated several challenges explorers will face when visiting an asteroid, including how to anchor to and move around the surface of a near-Earth object and how to collect samples of it.

NASA Asteroid Initiative Mission

NASA also has simulated an asteroid mission as part of its 2012 Research and Technology Studies ground test at Johnson. During the simulation, a team evaluated how astronauts might do a spacewalk on an asteroid and accomplish other goals. While performing a spacewalk on a captured asteroid will involve different techniques than the activities performed during recent analog exercises, decisions made about ways to best sample an asteroid will be informed by the agency’s on-going concept development and past work.

Scientific missions also have investigated the nature of asteroids to provide a glimpse of the origins of the solar system. From the Pioneer 10 spacecraft, which in 1972 was the first to venture into the Main Asteroid Belt, to the Dawn mission, which recently concluded its investigations of asteroid Vesta and is on its way to the dwarf planet Ceres, NASA's forays help us understand the origins of the solar system and inform decisions about how to conduct missions to distant planetary bodies. Scientists both at NASA and across the world also continue to study asteroids to shed light on their unique characteristics.

As NASA ventures farther into the solar system, the agency continues to simulate and evaluate operations and technical concepts for visiting an asteroid.

The M6.5 flare on the morning of April 11, 2013, was also associated with an Earth-directed coronal mass ejection (CME), another solar phenomenon that can send billions of tons of solar particles into space and can reach Earth one to three days later. CMEs can affect electronic systems in satellites and on the ground. Experimental NASA research models show that the CME began at 3:36 a.m. EDT on April 11, leaving the sun at over 600 miles per second.

Image above: The joint ESA/NASA Solar Heliospheric Observatory (SOHO) captured this series of images of a coronal mass ejection (CME) on the morning of April 11, 2013 over the course of 3:48 EDT to 4:36 EDT. Mars can be seen on the left. Credit: ESA&NASA/SOHO/GSFC.

Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they connect with the outside of the Earth's magnetic envelope, the magnetosphere, for an extended period of time.

The recent space weather also resulted in a weak solar energetic particle (SEP) event near Earth. These events occur when very fast protons and charged particles from the sun travel toward Earth, sometimes in the wake of a solar flare. These events are also referred to as solar radiation storms. Any harmful radiation from the event is blocked by the magnetosphere and atmosphere, so cannot reach humans on Earth. Solar radiation storms can, however, disturb the regions through which high frequency radio communications travel.

Image above: SOHO also captured this coronagraphic (a telescopic attachment designed to block out the direct light from a star so that nearby objects can be seen) image of the CME as it moves further out into the heliosphere. Credit: ESA&NASA/SOHO/GSFC.

NOAA's Space Weather Prediction Center (http://swpc.noaa.gov) is the United States Government official source for space weather forecasts, alerts, watches and warnings. NASA and NOAA – as well as the US Air Force Weather Agency (AFWA) and others -- keep a constant watch on the sun to monitor for space weather effects such as geomagnetic storms. With advance notification many satellites, spacecraft and technologies can be protected from the worst effects.

Image above: NASA's Solar Dynamics Observatory captured this image of an M6.5 class flare at 3:16 EDT on April 11, 2013. This image shows a combination of light in wavelengths of 131 and 171 Angstroms. Credit: NASA/SDO.

The sun emitted a mid-level flare, peaking at 3:16 a.m. EDT on April 11, 2013.

Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel. This disrupts the radio signals for as long as the flare is ongoing, anywhere from minutes to hours.

This flare is classified as an M6.5 flare, some ten times less powerful than the strongest flares, which are labeled X-class flares. M-class flares are the weakest flares that can still cause some space weather effects near Earth. This flare produced a radio blackout that has since subsided. The blackout was categorized as an R2 on a scale between R1 and R5 on NOAA’s space weather scales.

SOHO spacecraft. Image credit: NASA / ESA

This is the strongest flare seen so far in 2013. Increased numbers of flares are quite common at the moment, since the sun's normal 11-year activity cycle is ramping up toward solar maximum, which is expected in late 2013. Humans have tracked this solar cycle continuously since it was discovered, and it is normal for there to be many flares a day during the sun's peak activity.

Updates will be provided as need on the flare and its associated coronal mass ejection (CME), another solar phenomenon that can send solar particles into space and affect electronic systems in satellites and on Earth.

Dramatic underground explosions, perhaps involving ice, are responsible for the pits inside these two large martian impact craters, imaged by ESA’s Mars Express on 4 January.

The ‘twin’ craters are in the Thaumasia Planum region, a large plateau that lies immediately to the south of Valles Marineris, the largest canyon in the Solar System.

The northernmost (right) large crater in this scene was officially given the name Arima in early 2012, but the southernmost (left) crater remains unnamed. Both are just over 50 km wide and display intricate interior features.

Inside a central pit crater

The southernmost crater is also presented here in a perspective view, revealing its complex characteristics in detail.

Multiple terraces slump from the crater walls onto a flat floor, but perhaps the most striking feature is the central pit, a feature it shares with Arima crater to its north.

Central pit craters are common on Mars, as well as on the icy moons orbiting the giant planets in our Solar System. But how did they form?

When an asteroid hits the rocky surface of a planet, both it and the surface are compressed to high densities. Immediately after the impact, the compressed regions rapidly depressurise, exploding violently.

Arima twins in context

In low-energy impacts, a simple bowl-shaped crater results. In more dramatic events, larger craters are produced with more complex features, such as uplifted central peaks or sunken pits.

One idea for central pit formation is that when rock or ice melted during the impact drains away through fractures beneath the crater, it leaves a pit.

Another theory is that subsurface ice is rapidly heated, vapourising in an explosion. As a result, the rocky surface is excavated forming an explosive pit surrounded by rocky debris. The pit is in the centre of the main crater, where most of the impact energy was deposited.

Arima twins topography

Though the large craters in this scene have similar diameters, their central pits are rather different in size and depth, as is clearly evident in the topographical map. Compared to the Arima crater, perhaps more subsurface ice was present and more readily vapourised in the southern crater, punching through slightly thinner crust to leave a larger pit.

Many neighbouring small impact craters also show evidence for subsurface water or ice at the time of impact as evidenced by their ‘rampart’ ejecta blankets.

Ejecta blankets are debris deposits surrounding the crater, excavated from inside the crater during its formation. They have petal-like lobes around their edges: these result from liquid water bound up in the ejected material, allowing it to flow along the surface and giving it a fluid appearance.

Arima twins in 3D

Impact craters like these can thus provide windows into the past of a planet’s surface. In this case, they provide evidence for the Thaumasia Planum region having once hosted plentiful subsurface water or ice that was liberated during impact events both small and large.

mercredi 10 avril 2013

This artist's concept illustrates how charged water particles flow into the Saturnian atmosphere from the planet's rings, causing a reduction in atmospheric brightness. Image credit: NASA/JPL-Caltech/Space Science Institute/University of Leicester.

A new study tracks the "rain" of charged water particles into the atmosphere of Saturn and finds there is more of it and it falls across larger areas of the planet than previously thought. The study, whose observations were funded by NASA and whose analysis was led by the University of Leicester, England, reveals that the rain influences the composition and temperature structure of parts of Saturn's upper atmosphere. The paper appears in this week's issue of the journal Nature.

“Saturn is the first planet to show significant interaction between its atmosphere and ring system," said James O’Donoghue, the paper's lead author and a postgraduate researcher at Leicester. “The main effect of ring rain is that it acts to 'quench' the ionosphere of Saturn. In other words, this rain severely reduces the electron densities in regions in which it falls."

O’Donoghue explains that the ring's effect on electron densities is important because it explains why, for many decades, observations have shown those densities to be unusually low at certain latitudes on Saturn. The study also helps scientists better understand the origin and evolution of Saturn's ring system and changes in the planet's atmosphere.

"It turns out that a major driver of Saturn's ionospheric environment and climate across vast reaches of the planet are ring particles located some 36,000 miles [60,000 kilometers] overhead," said Kevin Baines, a co-author on the paper, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The ring particles affect both what species of particles are in this part of the atmosphere and where it is warm or cool."

In the early 1980s, images from NASA's Voyager spacecraft showed two to three dark bands on Saturn, and scientists theorized that water could have been showering down into those bands from the rings. Those bands were not seen again until this team observed the planet in near-infrared wavelengths with the ,W.M Keck Observatory on Mauna Kea, in Hawaii in April 2011. The effect was difficult to discern because it involves looking for a subtle emission from bright parts of Saturn. It required an instrument like that on Keck, which can split up a large range of light.

NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech

The ring rain's effect occurs in Saturn's ionosphere, where charged particles are produced when the otherwise neutral atmosphere is exposed to a flow of energetic particles or solar radiation. When the scientists tracked the pattern of emissions of a particular hydrogen ion with three protons (triatomic hydrogen), they expected to see a uniform planet-wide infrared glow. What they observed instead was a series of light and dark bands – with areas of reduced emission corresponding to water-dense portions of Saturn’s rings and areas of high emission corresponding to gaps in the rings.

They surmised that charged water particles from the planet’s rings were being drawn towards the planet along Saturn's magnetic field lines and were neutralizing the glowing triatomic hydrogen ions. This leaves large “shadows” in what would otherwise be a planet-wide infrared glow. These shadows cover some 30 to 43 percent of the planet's upper atmosphere surface from around 25 to 55 degrees latitude. This is a significantly larger area than suggested by images from NASA’s Voyager mission.

Both Earth and Jupiter have an equatorial region that glows very uniformly. Scientists expected this pattern at Saturn, too, but they instead saw dramatic differences at different latitudes.

"Where Jupiter is glowing evenly across its equatorial regions, Saturn has dark bands where the water is falling in, darkening the ionosphere," said Tom Stallard, a paper co-author at Leicester. "We're now also trying to investigate these features with an instrument on NASA's Cassini spacecraft. If we're successful, Cassini may allow us to view in more detail the way that water is removing ionized particles, such as any changes in the altitude or effects that come with the time of day."

Keck observing time was funded by NASA, with a letter of support from the Cassini mission to Saturn. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena, Calif.

A new study based on data from ESA's Cluster mission has revealed the importance of bursty bulk flows (BBFs) - fast streams of plasma that are launched towards Earth during the magnetic substorms that give rise to bright aurorae. By modelling these fast plasma streams using a kinetic approach, scientists have discovered that earlier studies based on magnetohydrodynamics tended to underestimate their role in the energy transfer during magnetic substorms. The new, more accurate description suggests that BBFs can carry up to one third of the total energy transferred during a substorm; in such cases, BBFs represent a major contributor to the brightening of aurorae.

The light show of aurorae has been observed close to Earth's polar regions for millennia, and for centuries a link between their occurrence and the activity of the Sun was apparent. Only with the aid of satellite-based measurements in the late twentieth century, however, could scientists begin to tackle the physical mechanisms causing this spectacular phenomenon.

Bright aurorae arise during magnetic substorms, violent events in Earth's magnetic environment, the magnetosphere. Substorms result from variations in the solar wind, the stream of electrically charged particles released by the Sun. When the solar wind changes in such a way as to invert the orientation of the interplanetary magnetic field, the tail of the magnetosphere gets compressed and blows powerful streams of highly-energetic plasma both towards Earth and in the opposite direction. As a consequence, plasma particles can infiltrate the upper layer of Earth's atmosphere – the ionosphere – producing breath-taking aurorae but also disturbing telecommunication networks and GPS.

"While we can grasp quite well the overall picture underlying magnetic substorms and aurorae, we are still far from the detailed understanding that would allow us to predict phenomena in Earth's magnetosphere," says Jinbin Cao from the Space Science Institute at Beihang University in Beijing, China. "In our study, we tried to achieve a more accurate description of the magnetospheric plasma by applying an alternative approach to the analysis of bursty bulk flows (BBFs), which are very fast streams of particles launched towards Earth during a substorm," he adds.

One of the vexed questions in the study of magnetic substorms concerns how exactly energy is transported across the magnetosphere, and in particular to Earth, during these events. Exploiting data from ESA's Cluster mission, Cao and his collaborators have revealed the importance of BBFs, a previously neglected mechanism. Surprisingly, BBFs turned out to be a major player in the energy transfer during the magnetic substorm that was analysed in this study.

"BBFs are short-lived, lasting typically ten to twenty minutes, and previous studies considered their contribution to the total energy transferred in a substorm to be marginal, adding up to only 5 per cent," explains Cao.

"However, those investigations were based on a very approximate description of the dynamics of plasma in the magnetosphere. In our study, we have implemented a more detailed modelling of the plasma, which has allowed us to discover that BBFs can carry much larger amounts of energy than previously thought – up to 35 per cent of the total energy that eventually reaches Earth and can be measured during an aurora."

Studying the dynamics of plasma is notoriously complex, and even more so in the magnetic environment of our planet. Collision dominated plasmas, such as those in planetary ionospheres, are usually modelled in terms of magnetohydrodynamics (MHD), an approach which treats all particles in the plasma as part of a single fluid. In Earth's magnetosphere, however, the experimental constraints coming from in situ measurements are so precise that they reveal that the MHD approximation is not always applicable.

"Whereas MHD is satisfactory to study the behaviour of collision dominated plasmas in distant astronomical sources, it breaks down when we try to model collisionless plasma phenomena in Earth's magnetosphere," says co-author George Parks from the University of California, Berkeley, USA.

ESA's Cluster's four Spacecrafts Constellation. Credit: ESA

"Directly sampling the properties of particles in the magnetospheric plasma forces us to drop the MHD approach, which only describes average properties. Instead we must study the kinetic behaviour of the individual particles. After all," he adds, "it is in the deviations from the average picture that we can read the signature of the physical processes at play."

The analysis conducted by Cao and his colleagues is based on data collected with the Cluster Ion Spectrometry (CIS) experiment, as one of the four Cluster spacecraft crossed the tail of the magnetosphere during a magnetic substorm on 30 July 2002. On this occasion, the experiment detected a BBF streaming towards Earth at velocities up to 1800 km/s.

"The measurements performed with Cluster gave us a very precise view of the density and velocity of the ions in the plasma over a very broad range of energies," comments Iannis Dandouras from the Institut de Recherche en Astrophysique et Planétologie (CNRS) and Université Paul Sabatier in Toulouse, France, who is the principal investigator of the CIS experiment.

"The data revealed that a BBF cannot be described as a single fluid, but that it consists of at least two components: a fast flow of higher-energy ions, and a second component made up of less energetic and slower ions," he says.

The study conducted by Cao and his colleagues suggests that the role of BBF in substorm energy transport is more complicated than previously thought, since the velocity distribution of ions in the BBF must be taken into account as well as the usual MHD parameters that describe the fluid – density, velocity and pressure.

With these data, the scientists were able, for the first time, to assess the actual contribution of BBFs to the energetics of magnetic substorms. They calculated the energy transported by BBFs during the substorm that they analysed using the kinetic approach, which is larger than the value calculated within the MHD approximation and amounts to about one third of the total energy transferred during this particular substorm. Further studies of these phenomena in a larger number of events are ongoing; preliminary results suggest that, for most substorms, the energy transported by BBFs is larger when calculated using the kinetic approach rather than the MHD approximation.

"This result reveals how an approximate description of the magnetospheric plasma has long underestimated the importance of a major phenomenon such as bursty bulk flows and highlights the need to model space plasma with ever greater detail," says Matt Taylor, Cluster Project Scientist at ESA. "This will not only advance our understanding of space weather in Earth's magnetosphere, but it will also bring new insight into the study of plasma in a variety of astrophysical environments," he concludes.

Note for Editors:

This article is based on results described in the paper by J. Cao, et al., "Kinetic analysis of the energy transport of bursty bulk flows in the plasma sheet", 2013, Journal of Geophysical Research: Space Physics, 118; doi: 10.1029/2012JA018351.

The study presented here is based on data gathered with the Cluster Ion Spectrometry (CIS) experiment on board one of the four Cluster spacecraft (C1) on 30 July 2002.

Cluster is a constellation of four spacecraft flying in formation around Earth. It is the first space mission able to study, in three dimensions, the natural physical processes occurring within and in the near vicinity of the Earth's magnetosphere. Launched in 2000, it is composed of four identical spacecraft orbiting the Earth in a pyramidal configuration, along a nominal polar orbit of 4 × 19.6 Earth radii (1 Earth radius = 6380 km). Cluster's payload consists of state-of-the-art plasma instrumentation to measure electric and magnetic fields over wide frequency ranges, and key physical parameters characterising electrons and ions from energies of near 0 eV to a few MeV. The science operations are coordinated by the Joint Science Operations Centre (JSOC) at the Rutherford Appleton Laboratory, United Kingdom, and implemented by ESA's European Space Operations Centre (ESOC), in Darmstadt, Germany.

This intriguing new picture from ESO’s Very Large Telescope shows the glowing green planetary nebula IC 1295 surrounding a dim and dying star located about 3300 light-years away in the constellation of Scutum (The Shield). This is the most detailed picture of this object ever taken.

Stars the size of the Sun end their lives as tiny and faint white dwarf stars. But as they make the final transition into retirement their atmospheres are blown away into space. For a few tens of thousands of years they are surrounded by the spectacular and colourful glowing clouds of ionised gas known as planetary nebulae.

This new image from the VLT shows the planetary nebula IC 1295, which lies in the constellation of Scutum (The Shield). It has the unusual feature of being surrounded by multiple shells that make it resemble a micro-organism seen under a microscope, with many layers corresponding to the membranes of a cell.

The planetary nebula IC 1295 in the constellation of Scutum (The Shield)

These bubbles are made out of gas that used to be the star’s atmosphere. This gas has been expelled by unstable fusion reactions in the star’s core that generated sudden releases of energy, like huge thermonuclear belches. The gas is bathed in strong ultraviolet radiation from the aging star, which makes the gas glow. Different chemical elements glow with different colours and the ghostly green shade that is prominent in IC 1295 comes from ionised oxygen.

At the centre of the image, you can see the burnt-out remnant of the star’s core as a bright blue-white spot at the heart of the nebula. The central star will become a very faint white dwarf and slowly cool down over many billions of years.

Stars with masses like the Sun and up to eight times that of the Sun, will form planetary nebulae as they enter the final phase of their existence. The Sun is 4.6 billion years old and it will likely live another four billion years.

Zooming in on the planetary nebula IC 1295

Despite the name, planetary nebulae have nothing to do with planets. This descriptive term was applied to some early discoveries because of the visual similarity of these unusual objects to the outer planets Uranus and Neptune, when viewed through early telescopes, and it has been catchy enough to survive [1]. These objects were shown to be glowing gas by early spectroscopic observations in the nineteenth century.

This image was captured by ESO’s Very Large Telescope, located on Cerro Paranal in the Atacama Desert of northern Chile, using the FORS instrument (FOcal Reducer Spectrograph). Exposures taken through three different filters that passed blue light (coloured blue), visible light (coloured green), and red light (coloured red) have been combined to make this picture.

Notes:

[1] Even early observers such as William Herschel, who discovered many planetary nebulae and speculated about their origin and composition, knew that they weren’t actually planets orbiting the Sun as they did not move relative to the surrounding stars.

More information:

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

mardi 9 avril 2013

ESA’s Herschel space observatory has provided the first images of a dust belt – produced by colliding comets or asteroids – orbiting a subgiant star known to host a planetary system.

After billions of years steadily burning hydrogen in their cores, stars like our Sun exhaust this central fuel reserve and start burning it in shells around the core. They swell to become subgiant stars, before later becoming red giants.

At least during the subgiant phase, planets, asteroids and comet belts around these ‘retired’ stars are expected to survive, but observations are needed to measure their properties. One approach is to search for discs of dust around the stars, generated by collisions between populations of asteroids or comets.

Dust disc around Kappa Coronae Borealis

Thanks to the sensitive far-infrared detection capabilities of the Herschel space observatory, astronomers have been able to resolve bright emission around Kappa Coronae Borealis (κ CrB, or Kappa Cor Bor), indicating the presence of a dusty debris disc.

The star is a little heavier than our own Sun at 1.5 solar masses, is around 2.5 billion years old and lies at a distance of roughly 100 light years.

From ground-based observations, it is known to host one giant planet roughly twice the mass of Jupiter orbiting at a distance equivalent to the Asteroid Belt in our own Solar System. A second planet is suspected, but its mass is not well constrained.

Herschel’s detection provides rare insight into the life of planetary systems orbiting subgiant stars, and enables a detailed study of the architecture of its planet and disc system.

“This is the first ‘retired’ star that we have found with a debris disc and one or more planets,” says Amy Bonsor of the Institute de Planétologie et d’Astrophysique de Grenoble, and lead author of the study.

“The disc has survived the star’s entire lifetime without being destroyed. That’s very different to our own Solar System, where most of the debris was cleared away in a phase called the Late Heavy Bombardment era, around 600 million years after the Sun formed.”

Dr Bonsor’s team used models to propose three possible configurations for the disc and planets that fit Herschel’s observations of Kappa Cor Bor.

The first model has just one continuous dust belt extending from 20 AU to 220 AU (where 1 AU, or Astronomical Unit, is the distance between Earth and Sun).

By comparison, the icy debris disc in our Solar System – known as the Kuiper Belt – spans a narrower range of distances, 30–50 AU from the Sun.

In this model, one of the planets orbits at a distance of greater than 7 AU from the star, and its gravitational influence may sculpt the inner edge of the disc.

ESA’s Herschel space observatory

A variation on this model has the disc being stirred by the gravitational influence of both companions, mixing it up such that the rate of dust production in the disc peaks at around 70–80 AU from the star.

In another interesting scenario, the dust disc is divided into two narrow belts, centred on 40 AU and 165 AU, respectively. Here, the outermost companion may orbit between the two belts between a distance of about 7 AU and 70 AU, opening the possibility of it being rather more massive than a planet, possibly a substellar brown dwarf.

“It is a mysterious and intriguing system: is there a planet or even two planets sculpting one wide disc, or does the star have a brown dwarf companion that has split the disc in two?” says Dr Bonsor.

As this is the first known example of a subgiant star with planets and a debris disc orbiting it, more examples are needed to determine whether Kappa Cor Bor is unusual or not.

“Thanks to Herschel’s sensitive far-infrared capabilities and its rich dataset, we already have hints of other subgiant stars that may also have dusty discs. More work will be needed to see if they also have planets,” says Göran Pilbratt, ESA’s Herschel project scientist.

Note for Editors:

“Spatially Resolved Images of Dust Belt(s) Around the Planet-hosting Subgiant κ CrB”, by A. Bonsor et al. is published in the Monthly Notices of the Royal Astronomical Society, April 2013.

Observations were performed using the Herschel Photodetector Array Camera & Spectrometer at 100 μm and 160 μm.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

lundi 8 avril 2013

This image shows the first holes into rock drilled by NASA's Mars rover Curiosity, with drill tailings around the holes plus piles of powdered rock collected from the deeper hole and later discarded after other portions of the sample had been delivered to analytical instruments inside the rover. Image credit: NASA/JPL-Caltech/MSSS.

Mars has lost much of its original atmosphere, but what's left remains quite active, recent findings from NASA's Mars rover Curiosity indicate. Rover team members reported diverse findings today at the European Geosciences Union 2013 General Assembly, in Vienna.

Evidence has strengthened this month that Mars lost much of its original atmosphere by a process of gas escaping from the top of the atmosphere.

Curiosity's Sample Analysis at Mars (SAM) instrument analyzed an atmosphere sample last week using a process that concentrates selected gases. The results provided the most precise measurements ever made of isotopes of argon in the Martian atmosphere. Isotopes are variants of the same element with different atomic weights. "We found arguably the clearest and most robust signature of atmospheric loss on Mars," said Sushil Atreya, a SAM co-investigator at the University of Michigan, Ann Arbor.

SAM found that the Martian atmosphere has about four times as much of a lighter stable isotope (argon-36) compared to a heavier one (argon-38). This removes previous uncertainty about the ratio in the Martian atmosphere from 1976 measurements from NASA's Viking project and from small volumes of argon extracted from Martian meteorites. The ratio is much lower than the solar system's original ratio, as estimated from argon-isotope measurements of the sun and Jupiter. This points to a process at Mars that favored preferential loss of the lighter isotope over the heavier one.

This pair of images taken a few minutes apart show how laser firing by NASA's Mars rover Curiosity removes dust from the surface of a rock. Image credit: NASA/JPL-Caltech/LANL/CNES/IRAP/LPGNantes/CNRS/IAS.

Curiosity measures several variables in today's Martian atmosphere with the Rover Environmental Monitoring Station (REMS), provided by Spain. While daily air temperature has climbed steadily since the measurements began eight months ago and is not strongly tied to the rover's location, humidity has differed significantly at different places along the rover's route. These are the first systematic measurements of humidity on Mars.

Trails of dust devils have not been seen inside Gale Crater, but REMS sensors detected many whirlwind patterns during the first hundred Martian days of the mission, though not as many as detected in the same length of time by earlier missions. "A whirlwind is a very quick event that happens in a few seconds and should be verified by a combination of pressure, temperature and wind oscillations and, in some cases, a decrease is ultraviolet radiation," said REMS Principal Investigator Javier Gómez-Elvira of the Centro de Astrobiología, Madrid.

Dust distributed by the wind has been examined by Curiosity's laser-firing Chemistry and Camera (ChemCam) instrument. Initial laser pulses on each target hit dust. The laser's energy removes the dust to expose underlying material, but those initial pulses also provide information about the dust.

This illustration shows the instruments and subsystems of the Sample Analysis at Mars (SAM) suite on the Curiosity Rover of NASA's Mars Science Laboratory Project. Image credit: NASA/JPL-Caltech.

"We knew that Mars is red because of iron oxides in the dust," said ChemCam Deputy Principal Investigator Sylvestre Maurice of the Institut de Recherche en Astrophysique et Planétologie in Toulouse, France. "ChemCam reveals a complex chemical composition of the dust that includes hydrogen, which could be in the form of hydroxyl groups or water molecules."

Possible interchange of water molecules between the atmosphere and the ground is studied by a combination of instruments on the rover, including the Dynamic Albedo of Neutrons (DAN), provided by Russia under the leadership of DAN Principal Investigator Igor Mitrofanov.

For the rest of April, Curiosity will carry out daily activities for which commands were sent in March, using DAN, REMS and the Radiation Assessment Detector (RAD). No new commands are being sent during a four-week period while Mars is passing nearly behind the sun, from Earth's perspective. This geometry occurs about every 26 months and is called Mars solar conjunction.

Graphic above: As the Sample Analysis at Mars (SAM) suite of instruments on NASA's Curiosity Mars rover heats a sample, gases are released (or "evolved") from the sample and can be identified using SAM's quadrupole mass spectrometer. Image credit: NASA/JPL-Caltech.

"After conjunction, Curiosity will be drilling into another rock where the rover is now, but that target has not yet been selected. The science team will discuss this over the conjunction period." said Mars Science Laboratory Project Scientist John Grotzinger, of the California Institute of Technology, Pasadena.

NASA's Mars Science Laboratory Project is using Curiosity to investigate the environmental history within Gale Crater, a location where the project has found that conditions were long ago favorable for microbial life. Curiosity, carrying 10 science instruments, landed in August 2012 to begin its two-year prime mission. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the project for NASA's Science Mission Directorate in Washington.

dimanche 7 avril 2013

In the Amur region is a grand building. Here's spaceport "East": launch complex, airfield, oxygen and nitrogen plant, hydrogen plant, power supply system. And many more kilometers of roads and railways. In this case, the main difference between the "East" - its compactness. The area of ​​the future cosmodrome in Baikonur 10 times less.

New launch pad for Soyuz's

A new expedition to the ISS was launched from the banks of the river Zeya, with taiga Baikonur East. So the news will start in a few years. And it does not seem fantastic.

The foundation for the future of Russian space almost ready. A huge pit - the future gas outlet launch facility. Tons of iron and concrete when rockets are launched hundreds of times to withstand tremendous heat and shock. Launching Pad - a springboard for a great leap into the universe erected in three shifts. Now construction 4000, by the summer will be twice as much.

"Getting a timely manner to the construction of the launch complex, technical complex. Also, industrial construction sites, industrial and operational base and built the whole spaceport provided and maintained infrastructure, "- says the Deputy Chairman of the Government of the Amur region, Konstantin Chmarov. Forced his way through the taiga, railwaymen are steel highway in the sky.

Амурский космос - Amur space (in Russian)

For these paths on the launch pad ready to go fly a rocket. And according to the old tradition Baikonurskaya certainly on track under the heavy makeup put a coin for luck. The old traditions in a new place do not change.

"The fact that there was a military spaceport, I certainly did, but that will be used for peaceful purposes, this spaceport, it is certainly a big plus," - says a railway builder Alexander Bondarenko.

5 years ago when it was decided to close the military spaceport Free, here at the time, stopped living. But soon, a new name - East and a new sense - become a peaceful modern spaceport.

"In parallel with the creation of the technological infrastructure, and maybe faster pace will need to solve social problems. There has to be built a new modern city in all respects, comfortable for the people who will live here and work, "- Vladimir Putin.

Image above: Vladimir Putin, President of the Russian Federation front the model of the new Amur space center.

3 years ago on the future of the spaceport was only a windbreak and the first peg. Thus began the work of one and a half years ago. And now it is the main building of the Far East, on the scale - almost legendary BAM. The former garrison Uglegorsk will become the new science city, with a population of under 40,000 people. At the end of the year will begin construction of a large housing estate. The influx of people here have already begun.

"We are very serious and talk a lot about what the Baikonur pollution is not harmful to people's lives. There are no dangerous and harmful production. No production and storage of toxic components of rocket fuel ", - says Konstantin Chmarov.

How to say the environmentalists, the taiga from the Baikonur hurt. The famous royal rocket "Soyuz", or rather its modern modification - environmentally friendly rocket. Moreover, most of the way to the orbit of the "union" will fly over the ocean.

Amur space Soyuz launch-pad top view

"Today is a very complex process, it only begins at the cosmodrome" East ". Why? There is a coastal shelf, where we produce oil, there is a way of shipping, there is a nearby areas with Japan. Therefore, all questions are very complex, but they are solved. We solve these problems naturally together with the developers of launch vehicles ", - says Director General of FSUE" TSENKI "Alexander Fadeev.

Command "key to start" do not have to wait long. When closer to May in the forest the snow melts, the building will go much faster. But now we can see the scale of this enormous construction site - on the map of Russia will soon be the capital of the new space.

The Solar Impulse technical flights have begun! There will be at least 4 of them over the coming weeks. These flights are designed to check the aircraft’s maneuverability and responsiveness in preparation for this spring’s Across America mission – which will kick off starting May 1st. They are necessary to ensure proper functioning and overall safety of HB-SIA which has undergone full disassembly and reassembly in March for transport from Switzerland to the United States.

ACROSS AMERICA: HB-SIA REASSEMBLY

The first one took place Tuesday April 2nd and it was a success: HB-SIA demonstrated its usual behavior.

You want follow these flights? The adventure is only a click away! Just sign up today and you will receive automatic notifications of all upcoming technical flights directly in your inbox! Every flight will be presented with an interactive map on our website: http://solarimpulse.com/across_america/s/flighttests

HB-SIA SolarImpulse first test flight across America

All Solar Impulse flights are fully dependent on weather conditions. Because of the aircraft’s light weight and ultra-thin materials, strong winds, storms are to be avoided. For this reason, flights are confirmed only a day in advance and can be subject to change depending on the latest forecast.